Evaluation of Humic Acid and Naphthalene Acetic Acid for Improving Growth and Morphological Characteristics of Green Gram (Vigna radiata L.)

Abstract

Green gram (Vigna radiata L.) is a widely cultivated grain legume recognized for its high nutritional
value and its role in maintaining soil fertility and agricultural sustainability. A field experiment was
undertaken to investigate the effects of humic acid (HA), naphthalene acetic acid (NAA), and their
combined applications on the growth characteristics of green gram. The study was conducted using a
Randomized Block Design (RBD) consisting of sixteen treatment combinations, including a control,
with three replications. Morphological parameters such as plant height, number of branches per plant,
and dry matter accumulation were assessed at the harvest stage. The findings indicated that the
application of HA and NAA significantly enhanced plant growth compared with the untreated control.
The greatest plant height (55.00 cm) was obtained under treatments T3 and T7, while the control
treatment recorded the minimum height (42.00 cm). Branch production also responded positively to the
treatments, with T7 producing the highest number of branches (10.00 branches plant⁻¹), whereas the
control exhibited only 6.00 branches plant⁻¹. Treatments T3, T6, T8, T9, T12, and T13 also showed
superior branching performance with 9.00 branches plant⁻¹. A similar trend was observed for dry matter
production, where T3, T7, T9, and T13 recorded the highest dry weight (10.00 g plant⁻¹), compared
with 7.00 g plant⁻¹ in the control. The improvement in growth parameters can be associated with
enhanced nutrient availability, stimulation of physiological activities, increased photosynthetic
efficiency, and greater biomass production resulting from the application of HA and NAA. The results
clearly demonstrate that humic acid and naphthalene acetic acid, applied either alone or in combination,
contribute substantially to the improvement of vegetative growth and dry matter accumulation in green
gram. Among the treatments evaluated, T7, T3, and T13 consistently exhibited superior performance,
suggesting their suitability for promoting growth and enhancing productivity of green gram under field
conditions.